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Lai Jiangshan 5f6130fa52 tiny_rcu: Directly force QS when call_rcu_[bh|sched]() on idle_task 
For RCU in UP, context-switch = QS = GP, thus we can force a
context-switch when any call_rcu_[bh|sched]() is happened on idle_task.
After doing so, rcu_idle/irq_enter/exit() are useless, so we can simply
make these functions empty.

More important, this change does not change the functionality logically.
Note: raise_softirq(RCU_SOFTIRQ)/rcu_sched_qs() in rcu_idle_enter() and
outmost rcu_irq_exit() will have to wake up the ksoftirqd
(due to in_interrupt() == 0).

Before this patch		After this patch:
call_rcu_sched() in idle;	call_rcu_sched() in idle
				  set resched
do other stuffs;		do other stuffs
outmost rcu_irq_exit()		outmost rcu_irq_exit() (empty function)
  (or rcu_idle_enter())		  (or rcu_idle_enter(), also empty function)
				start to resched. (see above)
  rcu_sched_qs()		rcu_sched_qs()
    QS,and GP and advance cb	  QS,and GP and advance cb
    wake up the ksoftirqd	    wake up the ksoftirqd
      set resched
resched to ksoftirqd (or other)	resched to ksoftirqd (or other)

These two code patches are almost the same.

Size changed after patched:

size kernel/rcu/tiny-old.o kernel/rcu/tiny-patched.o
   text	   data	    bss	    dec	    hex	filename
   3449	    206	      8	   3663	    e4f	kernel/rcu/tiny-old.o
   2406	    144	      8	   2558	    9fe	kernel/rcu/tiny-patched.o

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2015-01-06 11:01:12 -08:00
..
bpf bpf: verifier: add checks for BPF_ABS | BPF_IND instructions 2014-12-05 21:47:32 -08:00
configs
debug kdb: replace strnicmp with strncasecmp 2014-10-14 02:18:25 +02:00
events Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2014-12-19 13:15:24 -08:00
gcov gcov: enable GCOV_PROFILE_ALL from ARCH Kconfigs 2014-12-13 12:42:51 -08:00
irq genirq: Prevent proc race against freeing of irq descriptors 2014-12-13 13:33:07 +01:00
locking locking/mutex: Don't assume TASK_RUNNING 2014-10-28 10:55:08 +01:00
power PM: Eliminate CONFIG_PM_RUNTIME 2014-12-19 22:55:06 +01:00
printk This code is a fork from the trace-3.19 pull as it needed the trace_seq 2014-12-13 14:04:41 -08:00
rcu tiny_rcu: Directly force QS when call_rcu_[bh|sched]() on idle_task 2015-01-06 11:01:12 -08:00
sched sched_show_task: fix unsafe usage of ->real_parent 2014-12-10 17:41:09 -08:00
time Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2014-12-19 13:29:20 -08:00
trace More ACPI and power management updates for 3.19-rc1 2014-12-18 20:28:33 -08:00
.gitignore
acct.c acct: eliminate compile warning 2014-10-09 22:26:04 -04:00
async.c kernel/async.c: switch to pr_foo() 2014-10-09 22:26:04 -04:00
audit_tree.c fsnotify: unify inode and mount marks handling 2014-12-13 12:42:53 -08:00
audit_watch.c audit: invalid op= values for rules 2014-09-23 16:37:53 -04:00
audit.c Merge branch 'upstream' of git://git.infradead.org/users/pcmoore/audit 2014-12-13 13:41:28 -08:00
audit.h audit: reduce scope of audit_log_fcaps 2014-09-23 16:37:51 -04:00
auditfilter.c Merge git://git.infradead.org/users/eparis/audit 2014-10-19 16:25:56 -07:00
auditsc.c new helper: audit_file() 2014-11-19 13:01:26 -05:00
backtracetest.c
bounds.c
capability.c
cgroup_freezer.c
cgroup.c cgroup: implement cgroup_get_e_css() 2014-11-18 02:49:52 -05:00
compat.c compat: nanosleep: Clarify error handling 2014-09-06 12:58:18 +02:00
configs.c
context_tracking.c sched: stop the unbound recursion in preempt_schedule_context() 2014-10-28 10:46:05 +01:00
cpu_pm.c
cpu.c cpu: Avoid puts_pending overflow 2014-11-03 19:21:01 -08:00
cpuset.c Merge branch 'for-3.19' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2014-12-11 18:57:19 -08:00
crash_dump.c crash_dump: Make is_kdump_kernel() accessible from modules 2014-08-25 15:42:19 -07:00
cred.c
delayacct.c
dma.c
elfcore.c
exec_domain.c
exit.c TTY/Serial driver patches for 3.19-rc1 2014-12-14 15:23:32 -08:00
extable.c ftrace/x86/extable: Add is_ftrace_trampoline() function 2014-11-19 15:25:26 -05:00
fork.c mm: use new helper functions around the i_mmap_mutex 2014-12-13 12:42:45 -08:00
freezer.c freezer: remove obsolete comments in __thaw_task() 2014-10-21 23:44:20 +02:00
futex_compat.c
futex.c futex: Fix a race condition between REQUEUE_PI and task death 2014-10-26 16:16:18 +01:00
groups.c userns: Don't allow setgroups until a gid mapping has been setablished 2014-12-09 16:58:40 -06:00
hung_task.c
irq_work.c percpu: Convert remaining __get_cpu_var uses in 3.18-rcX 2014-10-29 11:18:18 -04:00
jump_label.c
kallsyms.c kernel/kallsyms.c: use __seq_open_private() 2014-10-14 02:18:16 +02:00
kcmp.c kcmp: fix standard comparison bug 2014-09-10 15:42:12 -07:00
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt
kexec.c kexec: remove unnecessary KERN_ERR from kexec.c 2014-12-13 12:42:51 -08:00
kmod.c usermodehelper: kill the kmod_thread_locker logic 2014-12-10 17:41:17 -08:00
kprobes.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux 2014-12-11 17:30:55 -08:00
ksysfs.c
kthread.c kernel/kthread.c: partial revert of 81c98869fa ("kthread: ensure locality of task_struct allocations") 2014-10-09 22:25:51 -04:00
latencytop.c
Makefile kernel: res_counter: remove the unused API 2014-12-10 17:41:04 -08:00
module_signing.c
module-internal.h
module.c The exciting thing here is the getting rid of stop_machine on module 2014-12-18 20:55:41 -08:00
notifier.c
nsproxy.c bury struct proc_ns in fs/proc 2014-12-04 14:34:54 -05:00
padata.c
panic.c kernel: add panic_on_warn 2014-12-10 17:41:10 -08:00
params.c param: do not set store func without write perm 2014-12-18 12:38:51 +10:30
pid_namespace.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2014-12-16 15:53:03 -08:00
pid.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2014-12-16 15:53:03 -08:00
profile.c
ptrace.c exit: ptrace: shift "reap dead" code from exit_ptrace() to forget_original_parent() 2014-12-10 17:41:10 -08:00
range.c
reboot.c kernel: add support for kernel restart handler call chain 2014-09-26 00:00:06 -07:00
relay.c
resource.c x86: optimize resource lookups for ioremap 2014-10-14 02:18:22 +02:00
seccomp.c Merge branch 'x86-seccomp-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2014-10-14 02:27:06 +02:00
signal.c Merge branch 'x86-mpx-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2014-12-10 09:34:43 -08:00
smp.c Merge branch 'for-3.18-consistent-ops' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu 2014-10-15 07:48:18 +02:00
smpboot.c sched, smp: Correctly deal with nested sleeps 2014-10-28 10:56:24 +01:00
smpboot.h
softirq.c rcu: Remove "cpu" argument to rcu_note_context_switch() 2014-11-03 19:20:34 -08:00
stacktrace.c stacktrace: introduce snprint_stack_trace for buffer output 2014-12-13 12:42:48 -08:00
stop_machine.c
sys_ni.c syscalls: implement execveat() system call 2014-12-13 12:42:51 -08:00
sys.c x86, mpx: On-demand kernel allocation of bounds tables 2014-11-18 00:58:53 +01:00
sysctl_binary.c kernel: add panic_on_warn 2014-12-10 17:41:10 -08:00
sysctl.c As the merge window is still open, and this code was not as complex 2014-12-16 12:53:59 -08:00
system_certificates.S
system_keyring.c
task_work.c
taskstats.c kill f_dentry uses 2014-11-19 13:01:25 -05:00
test_kprobes.c
torture.c torture: Address race in module cleanup 2014-09-16 13:41:06 -07:00
tracepoint.c
tsacct.c
uid16.c groups: Consolidate the setgroups permission checks 2014-12-05 17:19:27 -06:00
up.c
user_namespace.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2014-12-17 12:31:40 -08:00
user-return-notifier.c scheduler: Replace __get_cpu_var with this_cpu_ptr 2014-08-26 13:45:45 -04:00
user.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2014-12-17 12:31:40 -08:00
utsname_sysctl.c
utsname.c copy address of proc_ns_ops into ns_common 2014-12-04 14:34:47 -05:00
watchdog.c Merge branch 'for-3.18-consistent-ops' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu 2014-10-15 07:48:18 +02:00
workqueue_internal.h
workqueue.c workqueue: allow rescuer thread to do more work. 2014-12-08 12:39:16 -05:00